CIS-FFA DO NOT ALTER MEMBRANE DEPOLARIZATION BUT BLOCK CA2-STIMULATEDSOMATOTROPH CELLS - SUGGESTION FOR A DIRECT CIS-FFA PERTURBATION OF THE CA2+ CHANNEL OPENING( INFLUX AND GH SECRETION IN KCL)

It has been reported that cis-unsaturated free fatty acids (cis-FFA) b lock intracellular Ca2+ rise in EGFR T17 and GH(3) cells by perturbing the generation of Ins(1,4,5)P-3. In the present work, it was found th at cis-FFA did not alter potassium-induced cell depolarization in GH(3 ) cells, while blocking Ca2+ rise and GH secretion. Interestingly enou gh, saturated or trans-unsaturated FFA exert the opposite actions, i.e ., they block cell depolarization without altering Ca2+ rise and hormo ne secretion. As depolarization activates GH(3) cells via direct openi ng of Ca2+ channels with no generation of intracellular mediators, the se results suggest that cis-FFA act by a direct perturbation of the Ca 2+ channel opening. (C) 1997 Elsevier Science B.V.